In manufacturing semiconductor devices it is desirable if not required to remove pollutants from the surface of a semiconductor substrate prior to performing other surface treatment operations. Substrate surface pollution may be generated for example during manufacture processes. The failure to remove environmental substrate pollution typically reduces manufacturing yields and negatively affects the quality of the final semiconductor devices.
Such surface pollution on a semiconductor substrate can be generated by or result from any substrate manufacturing or processing step from the beginning up to and including completion of the manufacturing process. The sources of such substrate pollution are numerous, and may include particles, organics, metallic materials, oxide layers, such as a natural oxide of a substrate component, and many others. Because of the multiple sources of substrate pollution and the many possible types of pollutants, there is a limit to the completeness and effectiveness of prior art decontamination techniques.
At the same time, if a gate oxide layer is formed on a semiconductor substrate without such prior decontamination, the result will almost certainly be a defective semiconductor device or a device of less than optimal quality.
Furthermore, if a gate oxide layer is formed on a semiconductor substrate that has not been effectively treated for removal of pollutants, the resulting gate oxide layer has a tendency to be relatively and undesirably thin along at least some portion. As a result, functional ions which have been implanted into a gate electrode polysilicon structure formed over the gate oxide layer may permeate through an abnormally thin gate oxide layer and, perhaps, even permeate through the semiconductor substrate. Thus, an abnormally thin gate oxide layer resulting from a failure to remove pollutants from a substrate surface prior to forming the gate oxide layer is likely to result in a defect in the final semiconductor device.